// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

// This file contains the definition of the IdAllocator class.

#ifndef GPU_COMMAND_BUFFER_CLIENT_ID_ALLOCATOR_H_
#define GPU_COMMAND_BUFFER_CLIENT_ID_ALLOCATOR_H_

#include <stdint.h>

#include <map>
#include <utility>

#include "base/compiler_specific.h"
#include "base/macros.h"
#include "gpu/gpu_export.h"

namespace gpu {

// A resource ID, key to the resource maps.
typedef uint32_t ResourceId;
// Invalid resource ID.
static const ResourceId kInvalidResource = 0u;

// A class to manage the allocation of resource IDs.
class GPU_EXPORT IdAllocator {
public:
    IdAllocator();
    ~IdAllocator();

    // Allocates a new resource ID.
    ResourceId AllocateID();

    // Allocates an Id starting at or above desired_id.
    // Note: may wrap if it starts near limit.
    ResourceId AllocateIDAtOrAbove(ResourceId desired_id);

    // Allocates |range| amount of contiguous ids.
    // Returns the first id to |first_id| or |kInvalidResource| if
    // allocation failed.
    ResourceId AllocateIDRange(uint32_t range);

    // Marks an id as used. Returns false if id was already used.
    bool MarkAsUsed(ResourceId id);

    // Frees a resource ID.
    void FreeID(ResourceId id);

    // Frees a |range| amount of contiguous ids, starting from |first_id|.
    void FreeIDRange(ResourceId first_id, uint32_t range);

    // Checks whether or not a resource ID is in use.
    bool InUse(ResourceId id) const;

private:
    // first_id -> last_id mapping.
    typedef std::map<ResourceId, ResourceId> ResourceIdRangeMap;

    ResourceIdRangeMap used_ids_;

    DISALLOW_COPY_AND_ASSIGN(IdAllocator);
};

} // namespace gpu

#endif // GPU_COMMAND_BUFFER_CLIENT_ID_ALLOCATOR_H_
